The present invention relates to a method catalyzed through enzymes for the production of lignin graft polymer in solutions in which the polymerization product yield under the effect of organic peroxide combinations is high. The formation of undesirable, non-grafted side components is extensively suppressed. Furthermore the invention also covers lignin graft polymerization products produced according to the above-mentioned method with improved biological degradation as well as their utilization as building blocks in condensation resins, as binding and agglomeration media, as thickening media, as auxiliary products in petroleum drilling (drill rinsing fluid) and conveying, as a suspension and dispersion medium, as well as an auxiliary medium in textile and fiber upgrading.
Lignin is a high-molecular material which occurs in lignifying plants and is produced as a side product in the production of cellulose. Depending on the type of wood, the molecular structure of the lignin varies, i.e. the phenyl propane structure varies in the quantity of methoxy and hydroxy groups. Only a small portion of the lignin is water soluble, and the much greater, non-water-soluble portion can be extracted through solvents such as acetone or dioxane for example. The technical production utilizes mainly the alkaline or sulfite fusion process of wood, in which the water-soluble alkali or lignin sulfonates are produced as well as the organosolve process, in which the lignin is extracted from the wood by means of a mixture of solvent and water. The molecular weight of lignin lies in a range of 1000 to 150,000.
Since most of the lignin has always been burnt up in cellulose plants in order to obtain energy, many modification attempts were made in the past in order to provide a wider utilization for this occurring raw material. Processes in which a combination with synthetic polymerization products in form of graft polymers were realized were of particular interest.
Thus U.S. Pat. No. 4,687,828 describes high-molecular lignin graft polymers which are produced in polar, aprotic solvents with the utilization of the monomeric acrylamide and acrylamido-methylpropane sulfonic acid in a nitrogen atmosphere. As an initiator system a combination of calcium chloride, sulfuric acid, cer(IV) salt and auto-oxidation products of the dioxane (hydroperoxide) are used.
After a reaction period of 2 days at 30xc2x0 C. the polymerization product is precipitated and separated in a non-solvent. Polymerization product with greater purity and improved solubility are obtained by renewed solving in water, dialysis during several days and freeze-drying. No information is given on the grafting degree, but from the examples it appears that only about 40% in weight of the lignin mass used is recovered, and the loss in monomer ranges within an extraction loss of approximately 80%. Other monomer types are not used in this method. Graft polymerizates are proposed for utilization as thickeners, flooding polymers and drill rinsing additives.
J. J. Meister et al report on the synthesis and characterization of radically polymerized lignin/acrylamide graft polymers [Journal of Polymer Science; Polymer Chemistry Edition, Vol. 22, 1963-1980 (1984)]. The graft polymerizates produced according to the method of U.S. Pat. No. 4,687,828 contained between 19 and 49% in weight of non-grafter homopolymer.
EP 442 508 A1 discloses a method for the production of graft polymerization products from lignin or lignin-containing wood pulp and non-saturated acrylate or methacrylate monomers which carries out the graft reaction in a solution excluding oxygen in the presence of halogen salt and a hydrogen peroxide initiator. Grafting is to produce fillers and reinforcers compatible with plastics. To separate side products the mixture of grafted and non-grafted components is dialyzed, the product yield varies considerably. No information is given concerning the degree of grafting or the grafting yield, since the substances are not separated. Non-lignin components remain in any case non-grafted.
WO 94/01488 teaches a method for enzymatic polymerization/modification of lignin or lignin-containing materials in water with peroxide and hydrogen peroxide at alkalic pH values, without using organic solvents. The lignin thus modified has a higher molecular weight and is used as binding material for wood particle boards. Polymerization in the presence of synthetic monomers is not described.
A method of lignin grafting which is a considerable improvement over the state of the art is described in DE 43 31 878 A1. Using radically oxidized enzymes, all organic combinations containing at least three carbon atoms and one oxygen, nitrogen or multiple binding function can then be grafted on lignin in water, organic solvents or water/solvent mixtures. As a result it becomes possible for the first time to make graft polymers from lignin, unsaturated monomers and other organic combinations. The reaction times are shorter than with other grafting methods and no inert gas atmosphere is needed. As a substrate, hydrogen peroxide is supplied for peroxidases and oxygen for phenoloxidases. The polymerization product yield is low and amounts to only 26% according to example 4. The grafting yield is also low with this enzymatic polymerization method.
No enzymatic lignin grafting method is known in the state of the art which combines the advantages of this method with increased polymerization product or grafting yield.
The task was therefore to find a method for the enzymatic grafting of lignin, lignin-containing substances and lignin sulfonates, making it possible to obtain higher grafting yields or at least higher polymerization product yields than in the state of the art, in particular than DE 43 31 878 A1 and through which it is possible to carry out the technical methods within acceptable reaction times. A further task of the invention was to prepare graft products from lignin, lignin-containing substances and lignin sulfonates with hydrophilically neutral, anionic, cationic unsaturated monomers and/or other organic combinations which make possible utilization in water or an aqueous fluid, and are amenable to biological decomposition.
The task is accomplished surprisingly in that the graft polymerization catalyzed through oxidizing enzymes is carried out on lignin in the presence of organic peroxides/hydroperoxides. In this method surprisingly neither the enzymes are damaged by the organic peroxides nor is the homopolymer portion increased, as may be expected when peroxidic initiators are added. By comparison with the utilization of hydrogen peroxide or oxygen, it is possible to note a clear increase in the polymerization yield and the portion of grafted monomer in the graft polymer increases. It is obviously and surprisingly possible to reduce the peroxide to a much lesser degree through the utilization of the combination of organic peroxides and oxidizing enzymes.
The yield in graft polymerization product according to the method of the invention is high and amounts preferably to more than 50% in weight, and more preferably over 60% in weight and most preferably over 75% in weight.
The graft polymerization products have an unexpected suitability for biological decomposition which is apparent through a decomposition of the molecular weight following the action of basidomycetes causing pocket rot. Following an incubation time of 48 days, the molecular weight is reduced by at least 50% through biological decomposition.
The utilization of organic peroxides with the enzymatic grafting has proven to be a decisive factor in increasing the grafting yield. Assuming its solubility in the solvent or solvent mixture used for grafting, the organic peroxides are used in quantities, as related to the monomers used, of 0.01 % in weight to 10% in weight, preferably of 0. 1% in weight to 5% in weight and most preferably of 0.25% in weight to 1.5% in weight. Organic aliphatic, cyclo-aliphatic and aromatic peroxides to be mentioned as examples are t-butylhydroperoxide, mono and dihydroxyperoxide of dioxane, acetylcyclohexanesulfonylperoxide, diacetylperoxidicarbonate, dicyclohexylperoxidicarbonate, di-2-ethylhexylperoxidicarbonate, tert.-butylperneodecanoate, tert.-butylperpivalate, dioctanoyl peroxide, dilauroyl peroxide, dibenzoyl peroxide, tert.-butylper-2-ethyl-hexanoate, tert-butylpermaleinate, bis-(tert.-butylperoxide)-cyclohexane, tert-butylperoxiiospropylcarbonate, tert.-butylperacetate, 2,2xe2x80x2-bis-(tert.-butylperoxi) butane, dicumylperoxide, di-tert.-butylperoxide, di-tert.-amylperoxide, pinanhydroperoxide, p-methanehydroperoxide, cumolhydroperoxide, peroxyphthalate. t-Butylhydroperoxide and mono and dihydroxyperoxide of dioxane are especially preferred.
The utilization of redox co-initiators can have a positive effect on the polymerization product and grafting yield. For example, the heavy metal salts of copper, cobalt, iron, manganese, nickel and chrome should be mentioned, whereby Fe2+ and Mn2+ have proven themselves especially well. Reducing components, such as ascorbinic acid, sodium sulfite, sodium bisulfite, sodium formaldehyde sulfoxylate lead to clear reduction of the polymerization activity. The added utilization of redox co-initiators makes it possible to carry out the polymerization at lower temperature. The quantities of redox-co-initiators normally used amount to approximately 0.01 to 5% with reducing compounds and 0.1 to 100 ppm, preferably 0.5-10 ppm with heavy metals.
The lignin-modifying enzymes to be used according to the invention consist of oxidase, e.g. laccase, lignin peroxidase, mn peroxidase or their mixtures. Laccase is preferably used. The concentrations of enzyme used may vary widely and depends among other things on the enzyme type and the initiator system used, as well as on the number of phenoxy radicals to be produced. Depending on the monomers used, guideline concentrations are 200 to 0.1 U per g of monomer, preferably 100 to 1 U per g of monomer and most preferably 25 to 1 U per g. Of monomer. The enzyme quantity which converts I mMol substrate per minute is defined as enzyme unit U.
To improve the solubility of the enzymes in organic solvents, these may be integrated into enzyme matrix complexes. Such enzyme matrix complexes and their production are described in EP 354 485.
As a grafting base, lignin, lignin derivates, lignin-containing materials are used according to the invention, in particular the lignin and lignin sulfonate of different vegetal origin and with different molecular weights. Ullman""s Encyclopedia of industrial Chemistry (5th ed. 1990, Vol 15) contains an overview regarding lignin which can also be used with the grafting method according to the invention. Based on the sulfonate groups, lignin sulfonate-based grafted polymers possess improved solubility in water as compared with products based on sulfonate-free lignin. Depending on the application intended for the graft polymers, the spectrum ranges from low-molecular crystallization inhibitors for hard water component to high-molecular flocculents and thickeners as well as to cross-linked super-absorbers, with lignin of different molecular weights is used for grafting.
The portion of lignin components in the monomer mixture may fluctuate within wide limits, but should not exceed 50%, as this results in lower yields and molecular weights. In order to obtain high molecular weights over 200,000 it is often advantageous to prevent the quantity of lignin from exceeding 25% in weight, preferably 15% in weight, and most preferably 10% in weight.
The augmentation of the lignin portion in the reaction mixture also results in increased integration of the lignin in the graft polymer. Using UV-vis-spectrum of the GPC eluate of graft polymers it was possible to show that this was not just one mixture of graft and lignin homopolymer, but that grafting takes place over all the lignin portions.
In cases of insufficient solubility of the lignin components in the reaction medium it is possible, through the addition of tensides, to still render the lignin derivate accessible to the grafting reaction. The selection of the tenside or tensides is determined on the one hand by the structure of the lignin components and on the other hand on the composition of the reaction medium and is carried out in accordance with methods with which the person schooled in the art would be familiar.
Based on the enzymatic grafting method according to the invention, a great number of unsaturated organic compounds can be used for the grafting on the lignin component. In form of unsaturated compounds, the following anionic, cationic and neutral water-soluble monomer building blocks or their mixtures mentioned under a) to d) can be used for the enzymatic grafting. The enzymatic grafting also makes possible co-polymerization with the hydrophobic monomer building blocks mentioned under e). A whole spectrum of applications results already from the multiplicity of the monomers that can be used under the invention, since cationic, anionic as well as amphoteric graft polymerization products can be produced.
a) Water-soluble, acid-group-bearing, ethylenically unsaturated monocarbonic acids, its anhydrides and whose salts; sulfonic acid such as unsaturated dicarbonic acid, its anhydrides as well as their half-esters or half-amides. As an example are mentioned (meth)acrylic acid, (meth)allylsufonic acid, vinyl ethanoic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinylsulfonic acid, styrolsulfonic acid, vinylphosphonic acid, maleinic acid, fumaric acid, itaconic acid as well as half esters and half amides of the dicarbonic acids mentioned earlier, whereby the half-esters and half-amides are accessible to amines and amino-alcohol through reaction of the corresponding acid anhydride with alcohol. Preferred monomers carrying acid groups are: acrylic acid, methacrylic acid, maleinic acid and maleinic acid anydride, acrylamido-2-methylpropanesulfonic acid and (meth)allysulfonic acid or their salts.
b) Among unsaturated compounds of the group b) are non-ionic water-soluble monomers, e.g. meth(acylamide), (meth)acrylnitrile, hydroxyethyl(meth)acrylate, N-vinylpyrrolidone, N-vinylimidazole, N-vinylacetamide, N-vinylformamide, N-vinyl-N-methylacetamide, N-methylol(meth)acrylamide as well as alkoxylated monomers to which one arrives either through alkoxylation of ethylanic unsaturated compounds carrying at least one hydroxy-or amino group, or else through the conversion of the aloxy adducts of saturated aliphatic, cycloaliphatic, aromatic alcohol, amine or thiole with ethylenic unsaturated carbonic acid, reactive carbonic acid derivates or allylhalogenides. Examples are ethylene and/or propylene oxide adducts of (meth)allylalcohol, (meth)alylamine as well as hydroxyethyl(meth)acrylate, possibly others converted with reactively saturated acid derivatives. In addition, reaction products of preferably one-sided end-locked ethyleneglycol, isopropylglycol, butylglycol as well as nonylphenol, isotridecanol with ethylene or propylene oxide and continued reaction of the alkylenoxide adducts with (meth)acrylic acid, allychloride or other reactive, unsaturated acid derivatives such as e.g. the acid hydrides, the acid halogenides or their acid esters should be mentioned. Among these adducts methoxypolyethylene glycol-(meth)acrylate, nonylphenolpolyglycol(meth)acrylate and allylalcohol, each with 5 to 30 ethylenoxide units are preferred.
c) As building blocks of the c) group, monomers are used which are able to lend a catonic charge to the graft polymer or which form amphoteric polymerizates in combination with anionic monomers. Examples for this are N,N-dimethylaminopropyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylamide, N,N-dimethylaminoethyl(meth)acrylate, whereby the amino nitrogen is possibly quaternated or neutralized. N,N-dimethylaminoethylacrylate and N,N-dimethylaminopropylacrilamide are utilized in preference.
d) To produce graft polymers capable of swelling in water but no longer water soluble or graft polymers with higher molecular count, ramified but still partially soluble, the utilization of cross-linking monomers may be necessary in limited quantities. These cross-linking substances are integrated in the polymerization during polymerization or are used subsequently to cross-link the already existing polymer molecules. All compounds which contain at least two ethylenically unsaturated double bonds and a group which is reactively functional with regard to the acid group, or several groups which are functionally reactive regarding the acid group can be used as interlinking agents. Examples for this are: methylenebisacrylamide, acrylate and methacyrlate of poyoles such as butandiol-diacrylate, hexandiol-dimethacrylate, polyethylenglycol-diacrylate and trimethylolpropantriacrylate and/or the acrylate and methacrylates of the oxalkylated mentioned polyoles such as oxalkylated trimethylopropantriacrylate. Furthermore di- and polyester of polyoles and oxethylated polyoles with unsaturated monocarbonic acid and/or polycarbonic acid such as (meth)acrylic acid esters of 1,2 propylene glycol pentaerythrite, glycerin and polyglycerin as well as monoester of unsaturated alcohol and ethoxylated unsaturated alcohol with unsaturated monocarbonic acid and/or monocarbonic acids such as (meth)allylacrylate and -methacrylate, mono(meth)allylmaleinate, (meth)allylpolyethyleneglycoletheracrylate and -methacrylate, (meth)allylitaconate, (meth)allylpolyethyleneglycolether-itaconate and mono(meth)allylpolyethylenglycolether-maleinate. In addition diallylacrylamide, diallyphthalate, diallyladipate, triallylcitrate and trimonoallylpolyethyleneglycolethercitrate. In addition allylether of di- and polyoles and their oxethylates, as well as the diallylether of ethylenglycol, diethylenglycol, polyethylenglycol, the triallylether of glycerin, oxethylated glycerin, trimethylolpropane and oxethylated trimethylolpropane, the tetraallylether of pentaerythrite and oxethylated pentaerythrite as well as tetraallyloxiethane and polyglycidylether such as for example ethylenblycoldiglycidether and glyceringlycidylether. In addition amines and/or their salts and amides with at least two ethylanically unsaturated alkyl groups such as di- and triallylamine and tetraallylammoniumchloride.
e) All monomers which can be co-polymerized with a), b), c) and d) can be used as monomers. They are used for further modification of the graft polymers and thereby make it possible to achieve optimal adaptation to the graft polymers which are to be used according to the invention. Consequently the monomers under d) may have a hydrophilic as well as a hydrophobic character. Examples are vinyl acetate, vinyl propionate, (meth)acrylic acid ester, versatic acid vinyl ester known as styrol.
The application characteristics of already pre-interlinked graft polymerization products can be improved in most cases significantly through a post-interlinking. This post-interlinking can be effected in principle with all moisture contents of the pre-interlinked polymer gel. In a preferred embodiment the polymer gel is dried up to a water content of 5-20% in weight, preferably a maximum of 10% in weight at temperatures in the range of 100-190xc2x0 C. Following this the dried material is ground into a polymerization product powder with a grain size in the range of 20-3000 xcexcm, preferably 150-850 xcexcm. The post-interlinking of the polymerization product takes place on the surface of the polymer particle with at least one double or multiple functional interlinking medium reacting with acid groups, preferably carboxyl groups, which is applied preferably in form of an aqueous solution. Polyol such as ethylenglycol, 1,2-propyleneglycol, 1,4 butandiol, glycerin, di- and polyglycerin, pentaerythrite, oxethylates of such polyole as well as its ester with carbonic acid or carbon dioxide is suitable as the post-interlinking medium. The addition of an esterification catalyst, e.g. p-toluolsulfonic acid or phosphoric acid is advantageous. Additional suitable interlinking media are di and polyglycidylether of polyole and plyethylenglycol and salts of multi-valent cations. The post-interlinkers are used in quantities of 0.01 to 20% in weight, preferably 0.1 to 10 and most preferably 0.1 to 3% in weight relative to the polymerization product.
The post-interlinking is normally carried out at temperatures in the range of 100-250xc2x0 C., preferably 150-200xc2x0 C. in a mixing aggregate, i.e. a Nara mixer. Highly reactive post-interlinkers can also be used at lower temperatures of 20 to 100xc2x0 C. Post-interlinking often takes place also on graft polymer particles suspended in inert solvents. The utilization of different post-interlinkers or multiple post-interlinking is possible.
Depending on the application-specific characteristics in the field of hygiene, mostly monomers carrying acid groups are used for the synthesis of interlinked superabsorbing polymers on the monomer side, and in an especially preferred embodiment acrylic acid and methacrylic acid, whereas superabsorbing polymers show in addition acrylamide, methacrylamide and monomer particles containing sulfonate in the plant cultivation. Flocculants and dispersion products are produced on anionic as well as on cationic monomer basis; acrylamide is used preferably as the co-monomer. The polymerization products used in the fields of water hardening and washing and cleaning products are preferably built up from monomers containing carboxylate groups, however in these areas, co-monomers containing sulfonate and alkoxylate groups have proven themselves.
In addition it is often advantageous if inorganic per-compounds are added, insofar as they do not interfere with the grafting reaction or reduce the grafting yield significantly. The addition of inorganic peroxides, in particular, towards the end of polymerization makes consistent reduction of the residual monomer contents possible, so that other expensive processes for their separation can be omitted. These per-compounds are activated to special advantage by adding reducing compounds. Examples of inorganic per-compounds to be used according to the invention are: Sodium peroxodisulfate, calciumperoxodisulfate, ammoniumperoxodisulfate, peroxyborate.
Instead of the inorganic peroxides mentioned before, azo-initiators can also be used advantageously. The following azo-initiators are listed as examples of initiators that can be used according to the invention: 2,2xe2x80x2-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2xe2x80x2-azobis-(methyl-N-phenylpropionamidine)dihydrochloride, 2,2xe2x80x2azobis-(2-methylpropionamidine)dihydrochloride, 2,2xe2x80x2-azobis-(2,4-dimthylvaleronitrile), 2,2xe2x80x2-azobis-(isobutyronitrile), dimethyl-2,2xe2x80x2-azobisisobutyrate.
The method according to the invention is carried out in water, organic solvents or in mixtures of water and solvents. Among others, the following can be used as solvent components: dimethylsulfoxide, acetone, dioxane, methylpyrrolidone or their mixtures. In case that a mixture of water and solvent is used, the ratio of water and solvent is of course determined also by the miscibility of the two components. In a preferred embodiment however, the share of water is more than 50% in weight. Working purely with water, without organic solvents, is especially preferred.
The graft polymerization can take place in normal polymerization reactors equipped with the necessary aggregates for stirring, measuring solid, fluid and gaseous materials, for heating and for cooling. The grafting base is placed in the reactor together with the enzymes and is then mixed immediately or in course of polymerization by the monomer components. It is often an advantage to also first add a small portion of the monomers and to measure the remainder over a longer period of time. If interlinked graft polymerization products are being produced, different polymerization devices such as reaction mixers or polymerization bands are accordingly required. The temperatures for enzymatic polymerization are limited upward by the temperature stability of the enzyme and downward by the activity of the enzyme or by the polymerization speed. Preferred ranges of the polymerization temperature are between 10 and 60xc2x0 C. and especially preferred between 20 and 50xc2x0 C. The polymerization period may fluctuate between 1 hour and 2 days, depending on the activity of the enzyme, of the phenol components, of the monomers and of the graft polymerization temperature.
An atmosphere of protective gas may be necessary during the polymerization in order to avoid radical chain breakage.
The pH value during the graft polymerization according to the invention can fluctuate within a range of 3 to 8, preferably 4 to 5. The point in time for the neutralization of the monomer components depends on the required pH value of the graft polymerization solution and may accordingly occur before, during or after polymerization, or neutralization may occur in partial steps continuously or discontinuously.
Inorganic or organic alkali and acids can be used as neutralization means, e.g. ammonia, ammonium hydroxide, alkali-hydroxide, -carbonate and -hydrogen carbonate, amines, alkylamines, alkanolamines, hydroxylamines, mineral acids, organic sulfonic acids.
The concentration of deposit may fluctuate during the graft polymerization and depends among others on whether high or low molecular weights are to be produced, whether great or small portions of monomers are present, whether interlinked or soluble graft polymers are to be produced or whether water, organic solvents or a mixture of water and solvents are used as the reaction medium. In any case care should be taken that the deposit concentration be laid out in such manner that the required optimal graft polymerization temperature can be maintained.
Due to the phenolic components, the graft polymerization products have a more or less distinct coloring, which may be reduced or eliminated if necessary by oxidative or reductive additions. In this context hydrogen peroxide, sulfite salts or phosphoric acid have proven to be good bleaches.
Upon completion of polymerization the soluble polymerization products are either taken to their application directly, or are isolated in form of powder in case of special requirements by removing the solvent (spray drying/evaporation/freeze-drying). Precipitation can also be achieved by adjusting the pH value and/or by adding non-solvents. For some application a dialysis for the removal of low-molecular portions has proven successful. Dialysis membranes with different exclusion limits are available for sale.
In principle, polymerization can also be carried out in form of a suspension polymerization, whereby the aqueous reaction phase is dispersed with the help of suspension stabilizers in an organic phase which may consist e.g. of cyclohexane, and is polymerized in form of this suspension. Following this, water can be distilled out of the suspension azeotropically and the solid polymerization particles can be filtered without problem out of the organic base and can be conveyed to their application following drying.
Interlocked graft polymerizates are reduced , torn apart and dried either after or even during polymerization, and are ground to a given particle size as required by their application.
The molecular weight median of the graft polymers can be influenced over a wide range and vary between 1000 and 10 million. Due to technical application requirements different molecular weights are necessary for different areas of application. Thus for example, very high-molecular polymerization products are used in the field of flocculation and concentration aides, and for water hardening, dispersion and drilling rinsing the polymers according to the invention are used with comparatively low molecular weights. The molecular weights of the grafting base on the one hand and the enzyme/monomer ratio on the other hand are essential control parameters for the molecular weight.
The graft polymerization products according to the invention can be used to advantage in many areas of application. Among these absorption of aqueous and organic liquids, the controlled release of previously absorbed substances, flocculation, water hardening, dispersion, concentration and agglomeration are to be mentioned in first rank.
For the absorption of aqueous and organic liquids, interlinked polymerization products are to be considered above all, a s these swell when absorbing the liquids and store them. The kind of monomers to be grafted and the selection and quantity of the interlinkers as well as, if applicable, post-interlinking can serve to control the absorption behavior of the polymerization products, in particular also the absorption behavior under load which is important for the utilization of the products in diapers. By using partially neutralized acidic monomers, hydrophilic polymerization products are produced which absorb water and aqueous liquids, in particular blood and urine and are especially well suited for applications in the sanitary sector (diapers, incontinence products), since, contrary to purely synthetic absorbers, they are biologically degradable. In addition, the hydrophilic absorbers are used for food packaging and water insulation of cables. Integration into absorbing flat formations is possible, and synthetic and/or natural fibers in form of fabric or fleece into which the absorbers according to the invention are incorporated are used preferably to build up these surface formations. In the agricultural area the absorbers according to the invention are effective as water storers in the root areas of plants.
The absorbing polymers can also release active ingredients previously added to them with delay over a long period of time. An example would be additions of insecticides or fertilizers which make it possible to fight insects continuously and effectively or provide for an automatic nutrient supply to the plants over a long period of time. It is especially advantageous with these applications that the absorbers according to the invention are biologically degraded at the end of their utilization.
In the area of flocculation products, the polymerizates according to the invention are used in their soluble form, whereby high molecular weights of over 1 million are preferred. Typical flocculation processes are carried out e.g. in municipal sewerage, industrial sewerage, in chemical/technical processes, e.g. for red-slurry flocculation or in paper production or in the preparation of drinking water. Depending on the flocculation task to be performed, the polymers according to the invention must be given an anionic, cationic or amphoteric character through the selection of the monomer components to be polymerized. The polymers according to the invention are used as flocculants in concentrations of 0.1 to 5000 ppm, preferably 0.1 to 1500 and most preferably 0.1 to 500 ppm, depending on the flocculation process.
When the polymers according to the invention are used as incrustation inhibitors in washing and cleaning products, their good complexing properties for multi-value ions, e.g. calcium, iron and magnesium, and on the other hand their good dispersion capability are great advantages. The latter capability keeps pollutants and precipitated hard-water components in suspension during the washing process. These characteristics also make it possible to use the polymerization products advantageously in the fiber and textile treatment, in particular in bleaching and dying baths as well as in the preparation of raw fibers and in desizing, where heavy metals and the dispersion of hard water components, accessory materials of raw fibers and excess dying pigments must also be complexed. In water circuits the polymerization products are used to prevent the precipitation of hard water. Washing and cleaning products normally contain 0.1 to 20% in weight, preferably 0.5 to 12% in weight of the polymers according to the invention. For water hardening, polymer concentration of 0.2 to 5000 ppm, and preferably 1 to 2000 ppm are used. In textile treatment 0.1 to 10, preferably 0.1 to 5 g of polymer is added per liter of liquor.
The good dispersion characteristics of the polymerization products according to the invention are also used for the production and stabilizing of dispersions of organic dying pigments and inorganic pigments (e.g. titan dioxide, calcium carbonate, talc) as well as for the dispersion of drilling slurry produced in drilling operations. The dispersion of organic dye pigments and inorganic pigments normally requires 1 to 20% in weight of polymer as related to the pigment, whereby the ratio of polymer and organic dying pigment may also come to 1:1 in some extreme cases.
For the water hardening and dispersion application the preferred molecular weights of the polymer according to the invention lies in the range below 100,000, preferably below 50,000 and most preferably below 25,000.
If the polymerization products according to the invention are used as thickeners for water or aqueous preparations, e.g. in color printing, paper slip coating, painting dispersions or in tert. petroleum drilling, high-molecular polymers are preferred, i.e. the molecular weights should be preferably above 1 million so that good thickening performance may take place. In pigment printing for example, up to 10 g of polymer per liter of printing paste is used, and in petroleum drilling up to 1000 ppm.
The polymers according to the invention are also suitable as binding and agglomerating media. The agglomeration of filter dust, soot, fine coal, ballast coal and other dust and powders should be mentioned, as well as the joining of wood materials and core sanding (casting).
The biological degradability of the graft polymerization products according to the invention is surprising, since in the past state of the art synthetic graft branches as well as phenolic graft bases, in particular lignin, were classified as non-degradable. The degradability of the graft polymerizates was examined through the action of basidomycetes provoking pocket rot and was evidenced by the decrease of the molecular weight.
The production and application of the polymerization products according to the invention are explained in further detail through the following examples.
List of the abbreviations used for monomers and initiators;
AMPS acrylamidomethyl propane sulfonic acid
t-BHP tert.-butyl hydroperoxide
DIMAPA dimethylaminopropyl acrylamide
MAS sodium methallysulfonate
MBAA methylene bisacrylamide
TMPTA trimethylolpropandiacrylate